Fish assemblages associated with net pen mariculture and an adjacent rocky habitat in the Port of Ashdod, Israel (eastern Mediterranean) - preliminary results

Abstract

       The present study compares the fish assemblage in the vicinity of fish net pen in the Port of Ashdod, Israel, with those fishes inhabiting the nearby rocky substrate, in order to determine the impact of the mariculture on the surrounding environment. Seven visual censuses were conducted during January 1995 - June 2000; in each census, the species' abundance in both habitats was recorded. A total of 41 species, belonging to 17 families, were recorded. Both fish assemblages revealed a high level of stability during the study. Species richness and similarity indices were relatively high in all censuses. The most abundant species associated with the net pen were: Siganus rivulatus, Liza ramada, Chelon labrosus and occasionally Boops boops. In the adjacent rocky habitat, the most abundant species were: Siganus rivulatus, Diplodus sargus, D. vulgaris and Thalassoma pavo. The net pens attracted schooling species, feeding on algae growing on the pens' nets and on food waste and other organic material discharged. No apparent harm to wild local fish assemblage was observed, probably due to the efficient exchange of water around the cages, resulting from the movement of ships in the harbor and the entrance of currents under the breakwater.